This invention is directed to electrical circuit breakers and, more particularly, to electrical circuit breakers having a trip mechanism including a magnetic device associated with a load terminal conductor.
Circuit breakers are generally old and well known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 5,898,146 and 5,341,191. Such circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high-level short circuit condition.
Molded case circuit breakers include a pair of separable contacts per phase which may be operated either manually by way of a handle located on the outside of the case or automatically in response to an overcurrent condition. Circuit breakers include an operating mechanism which is designed to rapidly open and close the separable contacts, thereby preventing a moveable contact from stopping at any position which is intermediate between a fully open or a fully closed position. Circuit breakers also include a trip mechanism having a sensing device that senses overcurrent conditions in the automatic mode of operation; a trip bar responsive to the sensing mechanism; a trigger mechanism; and a latching and releasing mechanism. During an overcurrent condition, the trip bar responds to the sensing mechanism and releases the trigger mechanism. The trigger mechanism releases the latching and releasing mechanism, which, in turn, releases the operating mechanism thereby opening the separable contacts.
A typical sensing device is a current transformer positioned around a conductor that is connected to a load terminal of the breaker. It is desirable to prevent electrical contact between the current transformer and the adjacent conductor to prevent unwanted circulating currents in the current transformer components. Prior art circuit breakers have used an insulating barrier that included an opening for receiving the load terminal conductor. To install the barrier, the load terminal conductor had to be completely detached so that the barrier could be slid onto the conductor. It would be desirable to provide a circuit breaker with an insulating barrier that could be installed without the need to detach the load terminal conductor, but would still isolate the current transformer from the load terminal conductor.